Fungi, bacteria, nematodes, viruses and insects can cause problems in soil designated for growing. This soil contamination will lead to the dying off of plants, growth rate problems, root problems and production decrease. The need for soil disinfestation is thus recognized as a manifest one.
Various disinfestation methods exist. Sterilization at greater than 100.degree. C. is a total biocide treatment. Pasteurization at 70.degree. C. will eliminate many pathogenic fungi and their specific survival forms.
Chemical treatments can be divided into two classes: total disinfectants and limited biocide or biostatic activity. Examples of total disinfectants which are used with higher financial risks involved include chloropicrin, methyl bromide and methylisocyanate. Limited activity biocides include dichloroprene.
Methyl bromide is an odorless gas which is delivered to soils with or without the use of a plastic tarpaulin. Methyl bromide is a primary fumigant for controlling nematodes, weeds and fungi primarily for tomatoes, ornamentals, tobacco, peppers, strawberries and forest seedlings. One advantage of methyl bromide as a fumigant is that it evaporates; however, at 50 gram/m.sup.2 methyl bromide leaves 10 to 20 ppm of bromide or bromine compounds as a residue in the soil.
However, due to the United States' participation in the Montreal Protocol, compounds that have a detrimental effect on the ozone layer will be banned as of Jan. 1, 2001. These compounds include chlorinated fluorocarbons (CFC's) and methyl bromide. The 150 countries party to the United National Montreal Protocol are acting globally on what is pledged to be a complete phase out of methyl bromide and CFC's.
The economic effects of this ban in the United States and particularly California and Florida are manifest. The economic losses to these two states may be profound and total $900 million if a new approved fumigant cannot be found in time to replace the methyl bromide.
To that end, an alternative fumigant that possesses attributes similar to methyl bromide (no toxic residue, efficacy, and ease of use/economics) must be found. This fumigant should leave no toxic soil residue, should be biodegradable, and should exhibit efficacy against a wide variety of soil pathogens, as well as insects and nematodes.
The present inventors have discovered means for employing acrolein as a soil fumigant. Acrolein is a known pesticide that is used to treat liquids containing slime-forming microorganisms. Acrolein has been found to effectively control bacteria such as Bacillus subtilis. Pseudomonas putrefaciens and Escherichia coli: fungi such as Penicillium italicum, Saccharomyces cereviseae and Helminthosporium turcicum: algae; macroinvertebrates, such as snails and clams; and aquatic plants and weeds. Acrolein is also more effective than other biocides, such as chlorine, in controlling macroinvertebrates and submerged, as well as floating, aquatic weeds and algae.
From an environmental point of view, acrolein is a good biocide because it is effective, detoxified readily and inexpensively, and is non-persistent. Water solutions of acrolein are readily and conveniently neutralized for disposal with sodium bisulfite. This reaction produces a non-toxic water-soluble salt. Acrolein is also neutralized by reacting with materials present in natural waters and is therefore self-neutralizing. Also, one major advantage over methyl bromide is that there is no residue left in the soil other than normal carbohydrate residuals, that can be readily assimilated by plants and other organisms.
The present inventors have also discovered that acrolein can be administered to soil as a fumigant while avoiding the usual effects of phytotoxicity, which would otherwise prevent its utilization, by the specific method of application.
U.S. Pat. No. 2,959,476 discloses a method of controlling aquatic life in aqueous systems. This method is directed particularly to aquatic weeds and comprises adding a toxic quantity of acrolein to the particular body of water.
U.S. Pat. No. 3,250,667 discloses a method of controlling microorganisms encountered in the manufacture of paper. This method employs acrolein to inhibit the formation of slime-forming and corrosion-promoting microorganisms in the aqueous system of a paper-manufacturing plant. Fungi and bacteria are the primary organisms responsible for slimes in papermaking aqueous systems.
U.S. Pat. No. 3,298,906 discloses the use of acrolein acetals to protect a variety of plants from plant parasitic nematodes. This patent also discloses that the acrolein acetals can be combined with other known fungicides to control a broader spectrum of fungi.
U.S. Pat. No. 3,380,462 discloses a special system to utilize acrolein in a safe manner. This apparatus provides for creating a controlled pressure zone in the liquid to be treated and adding the acrolein to that zone.
U.S. Pat. No. 3,690,857 discloses the use of acrolein diacetals in watery media to kill aquatic weeds and other undesired life forms. This method will control the growth of these aquatic organisms while avoiding killing the majority of the fish present.